Recipe 3.12. Curing Stubborn USB Devices

Problem

Your new USB device is discovered and becomes an "Unknown Device" or fails to work even if listed properly in Device Manager.

Solution

Try using hardware alternatives:

Connect USB 1.1 devices to USB 1.1 ports or hubs.
Connect USB 2.0 devices to USB 2.0 ports or hubs.
Connect the USB device to a root hub.
Connect the USB device to a powered hub.
Install a USB add-in PCI card to avoid motherboard and BIOS problems.

Discussion

If a new USB device is detected by Windows XP and the Found New Hardware Wizard appears, you at least know your system has some USB functionality. You need to resolve hardware issues with signal quality and compatibility proper timing and getting a clean signal between a USB device and host are critical. However, you do not have any control over the USB host device, how it handles signals, or how the BIOS or native device drivers handle the host components.

You can, however control the connection points to a certain extent, by choosing which port you connect the device to on your PC. Most USB 1.1 devices will work when connected to USB 2.0 ports and hubs, which should down-shift to USB 1.1 specifications, but you may find that using a USB 1.1 port or hub is required. As well, most USB 2.0 devices will work when connected to USB 1.1 ports and hubs, but the performance will drop to USB 1.1 specifications, so you'll want to use a USB 2.0 port or hub.

Devices that get their power from the USB connection must be provided the right voltage and adequate current capacity to function. While all USB ports provide power, not all of them provide enough power for all of the devices you want to use. Plain USB hubs get their power from the host port. This arrangement may not provide adequate power, so opting for powered hubs is a good choice. Fortunately, USB is quite expandable by adding or daisy-chaining hubs, and if each hub provides power, every device should get what it needs. If you have two or more devices that require a lot of power, such as web cameras, separate their connections to different hubs to avoid overloading a single powered hub. Without detailed testing in somewhat of a "lab environment" it is not easy to tell if a port or hub is really delivering the power it says it will, so it can be easier to simply change brands or models of hubs until you get adequate power.

Laptops and system boards with built-in USB hosts are subject to the whims of BIOS and device drivers. Using a PC card or PCI-based USB host adapter and appropriate driver can separate native hardware problems and give XP something you both can work with.

Problem

Solution

Discussion

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